This invention relates to a multi-beam photoelectric safeguard system and, more particularly, to a method of installing a safeguard system including main light emitting and detecting devices and sub light emitting and detecting devices and a method of adjusting their optical axes.
Multi-beam photoelectric safeguard systems, comprising a light emitting device including a plurality of aligned light emitting elements and a light detecting device including a plurality of corresponding photodetectors as one unit, are commonly employed to detect the intrusion of an optical obstacle in a wide detection area. Multi-beam photoelectric safeguard systems are typically used to make protective fences, i.e. light curtains, along boundaries of prohibited areas where machine tools, punching machines, pressing machines, casting machines, automatic controllers and the like are installed, so that, if a part of the body of an operator, for example, intrudes into such a prohibited area, the system detects the intrusion and immediately stops the machine and/or gives a warning signal.
Regarding relative placement between the light emitting device and the light detecting device of a multi-beam photoelectric safeguard system, in case a machinery 1 such as a press as shown in FIG. 1 includes a projecting portion 2 projecting toward the operator, one of solutions is to place the safeguard system 3 in a position beyond the proximal end of the projecting portion 2 where the safeguard system does not interfere the projection 2 at all.
This placement, however, increases the horizontal distance X1 from the work center O of the machinery 1 to the safeguard system 3 (light curtain), hence increases the total area for installment of the press, for example, including the area for its safeguard system, and therefore decreases the working efficiency of the press.
In case the machinery 1 includes the projecting portion 2 that projects toward the operator, another solution is to place the safeguard system 3 as shown in FIGS. 2 and 3. In the conventional example shown here, the safeguard system 3 (light curtain) is positioned close to the machinery 1, and rearranged beforehand to exclude from effective detection the zone 4 encountering the projecting portion 2, i.e. the zone 4 where some of optical axes 5 forming the light curtain are optically blocked by the projecting portion 2. That is, a blanking function, which excludes the zone 4 encountering the projection 2 as a non-detection area beforehand, permits the safeguard system 3 (light curtain) to be placed even at a position where it interferes the projecting portion 2.
In this configuration, since the protective fence, i.e. light curtain, can be positioned closely to the machinery 1 (X2 less than X1) so as to keep a safety distance as small as possible with respect to the machinery 1, the working efficiency can be improved.
However, this approach relying on invalidating some of the optical axes 5 in the zone 4 excludes the full extension of the zone 4 from detection, including a section or sections at one or both sides of the projecting portion, although there is equally the possibility that an optical obstacle intrudes into the prohibited are through that section. To compensate this defect, another safeguard measure has to be employed, such as, for example, covering each such section of the zone 4 with a physical fence 6 such as a metal plate or net as shown in FIG. 4.
Japanese Patent Laid-Open Publication No. S63-43099 proposes a multi-beam photoelectric safeguard system contemplating the existence of a projecting portion as discussed above. The safeguard system disclosed in this publication is comprised of a pair of light emitting and detecting devices including a plurality of light emitting elements and complementary photodetectors, respectively, and a pair of reflection mirrors disposed adjacent to the projecting portion so that, in the zone encountering the projecting portion, a light curtain is made at one or opposite sides of the projecting portion by reflecting light beams from the light emitting and detecting devices at the reflection mirrors and receiving the reflected light beams at the same light emitting and detecting devices.
With the safeguard system taught by that publication, however, it is difficult to adjust the optical axes between the light emitting and detecting devices and the optical alignment of respective light emitting elements and photodetectors with associated reflection mirrors. Especially when the optical axes are arrayed closely, the difficulty becomes greater. Furthermore, since each of the light emitting and detecting devices has to include light emitting elements or photodetectors for emitting or detecting light beams to and from the reflection mirrors, the light emitting and detecting devices inevitably become bulky.
It is therefore an object of the invention to provide a method of installation and a method of adjusting optical axes of a multi-beam photoelectric safeguard system capable of positioning a light curtain made of closely arrayed optical axes very closely to a machinery or equipment such as a press, which requires the safeguard system.
A further object of the invention is to provide a method of installation and a method of adjusting optical axes of a multi-beam photoelectric safeguard system which is suitable for use with a machinery or equipment such as a press, which requires the safeguard system and includes a portion projecting toward the operator, and can make a light curtain closely to the press with no invalidated zone.
A still further object of the invention is to provide a method of installation of a multi-beam photoelectric safeguard system for making a light curtain without non-detection zones around an interfering object by using a main light emitting device and a sub light detecting device operable according to a basic operation sequence to sequentially emit light beams from the main light emitting device at predetermined timings, which can simultaneously generate a new operation sequence incorporating sub light emitting and detecting devices as well.
Those objects of the invention can be accomplished by various aspects of the invention.
According to an aspect of the invention, there is provided a method of installing a multi-beam photoelectric safeguard system for making a light curtain with a number of light beams around an interfering object, the multi-beam photoelectric safeguard system including:
a main light emitting device having a plurality of light emitting elements aligned in an array at equal intervals;
a main light detecting device disposed in an opposed relationship with the main light emitting device and having a plurality of photodetectors equal in number to the light emitting elements and arranged in an array at regular intervals;
a sub light detecting device disposed adjacent to one side of the interfering object interrupting a light beam of at least one optical axis of the light curtain, and including at least one photodetector capable of detecting a light beam from the main light emitting device;
a sub light emitting device disposed adjacent to the other side of the interfering object and capable of emitting a light beam toward the main light detecting device; and
the light curtain including a main detection area defined between the main light emitting device and the main light detecting device, a first sub detection area defined between the main light emitting device and the sub light detecting device, and a second sub detection area defined between the sub light emitting device and the main light detecting device,
the method comprising:
(a) positioning the main light emitting device and the main light detecting device relative to each other and identifying a blanking optical axis interrupted by the interfering object among the light beams between the main light emitting device and the main light detecting device;
(b) placing the sub light detecting device adjacent to one side of the interfering object and thereafter positioning same relative to the main light emitting device by moving the sub light detecting device; and
(c) placing the sub light emitting device adjacent to the other side of the interfering object and thereafter positioning same relative to the main light detecting device by moving the sub light emitting device.
In a preferred embodiment of the invention, relative positioning of the main light emitting and detecting devices and adjustment of their optical axes may be carried out either without any interfering object or under the existence of such object.
In an embodiment of the invention, an optical axis adjustment display or optical axis adjustment display lamp is typically provided on the main light emitting device and/or main light detecting device. The operator can confirm completion of relative positioning of the main light emitting and detecting devices and adjustment of their optical axes by watching the optical axis adjustment display. Similarly for sub light detecting and emitting devices, an optical axis adjustment display or display lamp is preferably provided on the sub light detecting device and or sub light emitting device.
In another preferred embodiment, a controller for substantially controlling light emitting and detecting devices of the safeguard system may be provided, and an optical axis adjustment display or display lamp may be provided on the controller such that adjustment of optical axes of all light emitting and detecting devices contained in the safeguard system can be confirmed totally on the optical axis adjustment display of the controller.
In another preferred embodiment, the main light emitting and detecting devices forms a basic unit of the safeguard system, and sub light emitting and detecting devices may be added as an optional unit if a user requests. The main light emitting and detecting devices as the basic unit operate according to a preset basic operation sequence. In the basic sequence, light emitting elements contained in the main light emitting device are sequentially activated at predetermined timings for a predetermined length of time, individually.
When the sub light detecting and emitting devices are added to the main light emitting and detecting device activated by the basic operation sequence, by identifying the blanking optical axis, it is possible to automatically generate a modified operation sequence for additionally determining operations of the sub light emitting device on the basis of the blanking optical axis.
When optical axes are again adjusted upon maintenance after installation of the multi-beam photoelectric safeguard system suitable for use of the present invention, it is advantageous to first adjust optical axes between the main light emitting and detecting devices by moving them relative to each other, next adjust the optical axes between the main light emitting device and the sub light detecting device by moving the latter, and finally adjust optical axes between the sub light emitting device and the main light detecting device by moving the former.
As another method of optical axis adjustment, it is possible to first adjust optical axes between the main light emitting and detecting devices by moving them relative to each other, next adjust optical axes between the sub light emitting device and the main light detecting device by moving the former, and finally adjust the optical axes between the main light emitting device and the sub light detecting device by moving the latter.
These and other objects and advantages of the invention will appear from the following description of preferred embodiments mainly in conjunction with the accompanying drawings.